The invention generally relates to the field of computer graphical user interface systems. More particularly, the invention relates to user-manipulable apparatus for moving a symbol, such as a cursor, on a display, and for entering xe2x80x9cpoint and clickxe2x80x9d type user commands.
The invention has particular applicability to computer graphical user interface (GUI) apparatus, and can be used in systems which conventionally employ devices such as IBM Corporation""s TrackPoint III pointing devices, in keyboards of various IBM computer products. (IBM and TrackPoint III are registered trademarks of International Business Machines Corporation.)
The growing interactiveness of home entertainment systems, particularly cable television, interactive television, and Internet set-top boxes, is placing greater demands on hand-operated controls.
Mice have been commonly used as user-manipulable GUI apparatus. Using a mouse, a user directs the movement of a cursor across a display screen by corresponding manual mouse movements.
Joystick-type devices have also been used. In particular, IBM Corporation""s TrackPoint III pointing device (hereinafter xe2x80x9cTrackPoint-type devicexe2x80x9d or xe2x80x9cTrackPoint devicexe2x80x9d) has been mounted in-keyboard in many laptop computers. A TrackPoint-type device includes a button-like structure resembling a pencil eraser and disposed between keys of a computer keyboard, has facilitated the use of graphical user interfaces (GUIs) in portable computers. The need for a mouse, and a flat working surface on which the user manipulates the mouse, is eliminated, because the user is able to manipulate the TrackPoint device entirely within the keyboard.
A conventional physical implementation of the TrackPoint III pointing device is described in co-pending, co-assigned U.S. patent application Ser. No. 08/181,648, filed Jan. 4, 1994. That implementation includes strain gauge sensors, and a post serving as a lever arm. By manipulating the post, the user flexes the strain gauges. Small analog signals produced by the strain gauges are interpreted by on-board software, and the cursor is moved accordingly.
The strain gauges produce a xc2xd% full-scale signal change, and must be individually trimmed during manufacture to match their outputs. The manufacturing and trimming of the strain gauges, combined with the small analog signal they produce, contribute to the cost of the sensor, and of the electronics required to make a TrackPoint III system. Moreover, the small full-scale magnitude of the signal change places a burden on the data acquisition system which processes the strain gauge signals into cursor movement signals.
Therefore, an important objective in the design and manufacture of TrackPoint type devices is the reduction of these cost-adding factors.
These issues have been confronted in the design and manufacture of other types of user-manipulable electronic components. For instance, a conventional structure is taught in Hughes, U.S. Pat. No. 4,305,007, xe2x80x9cElectronic Two Directional Control Apparatusxe2x80x9d, issued Dec. 8, 1981. This patent describes a structure including four sensing electrodes, whose capacitances independently vary in response to the proximity of an external object.
A physical implementation of the Hughes structure is shown in FIG. 7 of the Hughes patent, which is reproduced as FIG. 1 of the present patent application. For simplicity, and to allow for a brief summary of the description of the Hughes structure, the reference numbers not directly pertinent to the summary have been deleted.
The Hughes structure includes sensing electrodes 5 that map out four quadrants. A controlling member 3 at the end of a displaceable member 2, supported from above by a ball joint 1, moves in relation to the sensing electrodes 5. These elements are contained within a three dimensional grounded shield box 4.
Note, however, that, in addition to being impractical for implementation in a keyboard or in a portable computer, the Hughes structure requires considerable cost for parts and assembly. Also, the manufacturing process must include manual trimming of the electronic circuit to match the outputs of the four quadrants. Therefore, the Hughes apparatus does not provide the desired low cost.
Accordingly, it is an object of the invention to provide cost reductions in the manufacture of TrackPoint-type user-manipulable pointing devices which had not been realized in conventional structures.
To achieve this and other objects, there is provided in accordance with the invention an apparatus for sensing manipulation by a user and for producing signals related to the manipulation. The signals produced by such an apparatus may then be used as part of a user interface system. For instance, the signals might be used in a personal computer having a display screen, for causing movement of a displayed symbol, such as a cursor.
The apparatus essentially has two components. The first component includes an articulating member. Means are provided for causing the articulating member to articulate responsive to user manipulation thereof, and thereafter, to return to a quiescent position.
The second component includes a sensor array, made up of a plurality of sensing members disposed about the articulating member. Means are provided for detecting respective signals from the sensing members, the respective signals varying in value depending on articulation of the articulating member.
In accordance with the invention, these components are made up of inexpensive electrical components and simple mechanical components, to produce a low cost pointing device whose physical size and dimensions are suited for use in applications such as in-keyboard TrackPoint-type devices.
The sensing members preferably include flat, electrically conductive members on a planar substrate, such as etched conductive regions on a printed circuit board, and the articulating member includes an electrically conductive member whose varying proximity to the sensing members, due to the manipulation by the user, produces a correspondingly varying capacitance value. The magnitude of the capacitance is determined by a data acquisition system, preferably including RC oscillators and a microcontroller. In accordance with a suitable transfer function, the capacitance value is used to produce the cursor movement signals.
A device according to the invention may advantageously be employed as a pointing device for hand-held remote control applications, as well as for keyboards. Cost is a driving factor in the success of any device targeted to the consumer electronics market. The capacitive sensor and data acquisition system according to the invention (oscillator and microcontroller) provide advantageously low manufacturing costs.
The low-cost capacitive device according to the invention is also inherently less expensive than a mouse. Both pointing technologies require a microcontroller. In addition, a mouse requires two optical interrupters, two mechanical disks, a rotating ball, and a three dimensional structure to align these items. A preferred implementation of the capacitive sensor-based device according to the invention includes a conductive disk attached to the circuit board, and an inexpensive integrated circuit (Schmitt Trigger NAND). The invention uses fewer components, and is easier to manufacture and assemble. The absence of moving parts exposed to the environment means the invention has advantageously low maintenance, and a low failure rate.